A typical prior art head and disk system 10 is illustrated in block form in FIG. 1. In operation the magnetic transducer 20 is supported by the suspension 13 as it flies above the disk 16. The magnetic transducer 20, usually called a “head” or “slider,” is composed of elements that perform the task of writing magnetic transitions (the write head 23) and reading the magnetic transitions (the read head 12). The electrical signals to and from the read and write heads 12, 23 travel along conductive paths (leads) 14 which are attached to or embedded in the suspension 13. The magnetic transducer 20 is positioned over points at varying radial distances from the center of the disk 16 to read and write circular tracks (not shown). The disk 16 is attached to a spindle 18 that is driven by a spindle motor 24 to rotate the disk 16. The disk 16 comprises a substrate 26 on which a plurality of thin films 21 are deposited. The thin films 21 include ferromagnetic material in which the write head 23 records the magnetic transitions in which information is encoded.
Magnetic media for perpendicular recording include a magnetically soft underlayer which is relatively thick (>100 nm). The combination of thickness and the residual stresses in the films creates a driving force for delamination of the films. The deposition of an appropriate adhesion layer onto the substrate can reduce delamination.
In published U.S. patent application 20040146686 by Kim, et al., Jul. 29, 2004 an adhesion layer is described which is formed between the disk substrate and the soft magnetic layer. A material “containing Ti” is taught for use as an adhesion layer with a thickness range of 1-50 nm, but the only example of the adhesion layer is 100% Ti.
In published U.S. patent application 0040009375 by Tanahashi, et al. Jan. 15, 2004, a “pre-coat layer” is deposited onto the substrate which is said to be selected for good adhesion is described as being nickel 37.5 at. % tantalum 10 at. % with the remainder being Zr.
In published U.S. patent application 20020122959 by Matsunuma, Satoshi, et al., Sep. 5, 2002 an adhesive layer such as 5 nm of Ti may be formed on the substrate of the magnetic recording medium before forming the soft magnetic layer.
In published U.S. patent application 20020122958 by Tanahashi, Kiwamu, et al. Sep. 5, 2002, a material which shows adhesion with the substrate, has a flat surface and reacts little with the soft magnetic underlayer with annealing is used as the pre-coating layer for the substrate. Amorphous or nanocrystalline materials such as NiZr alloy, NiTa alloy, NiNb alloy, NiTaZr alloy, NiNbZr alloy, CoCrZr alloy and NiCrZr alloy can be used.
In U.S. Pat. No. 6,428,906 to Wong , et al., Aug. 6, 2002, an underlayer is described which can be close packed hexagonal (hcp) Ti or TiCr deposited to promote the growth of a hcp Co alloy perpendicular to the plane of the films. For perpendicular recording, a magnetically soft layer, for example, NiFe, is added to provide an image effect for the writing process. In a preferred embodiment of the invention, an underlayer deposited on top of the soft underlayer of NiFe is titanium aluminum (TiAl) preferably having a L10 lattice structure. The TiAl is not used as an adhesion layer in this case.
U.S. Pat. No. 5,589,262 to Kiuchi, et al., Dec. 31, 1996, describes an adhesion layer formed between the substrate and the underlayer which made of titanium (Ti) or chromium (Cr).
Published U.S. patent application 20030091798 by Zheng, Min, et al., May 15, 2003, uses an intermediate tantalum layer deposited between the soft magnetic layer and the substrate to improve adhesion of the soft magnetic layer to the substrate.
A beta-Ta layer between a silicon substrate and a NiFe layer serves as an adhesion layer in 4,632,883 Howard , et al. Dec. 30, 1986.